package com.cyh.structurealgorithm;

import java.util.Arrays;

public class FibonacciSearch {
    public static int maxSize = 20;
    public static void test() {
        int arr[] = {-8, -2, -2, -1, 3, 3, 5, 9, 10, 10, 11};
        int resIndex = fibSearch(arr, 9);
        System.out.println("查找的下标：resIndex = " + resIndex);
    }

    //生成一个斐波那契数列
    public static int[] fib() {
        int[] f = new int[maxSize];
        f[0] = 1;
        f[1] = 1;
        for(int i = 2; i < maxSize; i++) {
            f[i] = f[i - 1] + f[i - 2];
        }
        return f;
    }

    public static int fibSearch(int[] a, int key) {
        int low = 0;
        int high = a.length - 1;
        int k = 0;
        int mid = 0;
        int f[] = fib();
        while(high > f[k] - 1) {
            k++;
        }
        int[] temp = Arrays.copyOf(a, f[k]);
        for(int i = high + 1; i < temp.length; i++) {
            temp[i] = a[high];
        }
        while (low <= high) {
            mid = low + f[k-1] - 1;
            if(key < temp[mid]) {
                high = mid - 1;
                k--;
            } else if(key > temp[mid]) {
                low = mid + 1;
                k -= 2;
            } else {
                if(mid <= high) {
                    return mid;
                } else {
                    return high;
                }
            }
        }
        return -1;
    }
}
